MAZeT has developed an optical ASIC sensor that can be used, for instance, to test high-precision weld seams found on the nozzles of fuel injection systems.

The SISCAN system consists of two components: the sensor board and the interface board. The former contains the ASIC sensor and the controller, while the latter establishes the interface with a host computer via USB 2.0 and controls the measurement system’s laser light source. The key components of the sensor board are the ASIC sensor (controlled by an FPGA logic) and four high-speed AD converters, whereby the information outputted by these is temporarily stored in registers. The sensor board based on chip-on-board (COB) technology features a high packing density and a specially designed opto-sensor array (ASIC sensor). The ASIC sensor has a photocurrent range of 0.5 nA–2 μA, offers a processing speed (for channel measurement) of 300 kHz, features a settling time for the reading of measured values of roughly 400 ns, and provides high channel synchronicity.

Optical measuring and testing

When deployed for measuring and testing, the SISCAN sensor uses a high-precision confocal measurement system to determine the surface roughness. Here, a laser beam gradually scans the surface of the component that is being measured. Split into 128 separate beams, the laser beam strikes the surface over a length of approximately 16 mm (x-direction). Using a tuning fork, the focus of each beam is shifted slightly at a vertical angle to the surface (z-direction) and the reflected light is then captured by the sensor. To obtain the most powerful light signal, the focus and surface must converge exactly. The height profile for a section of the component’s surface is created based on the intensity of the signal. The entire surface can be scanned by gradually moving the laser and sensor over it. With 128 measuring channels, MAZeT’s ASIC sensor is able to record in parallel all peak values of the 128 signals from the separate laser beams. In addition to the 128 pixels, which take the form of PIN photodiode lines, the IC also includes a reference channel. The chip length (linear dimension) is predetermined based on the fixed arrangement of the laser beams. As a result, the total surface of the chip is approximately 100 mm². A low-noise amplifier, a logarithmic and a repeater amplifier are integrated into the ASIC sensor for each pixel for use in analyzing and processing the laser light signals captured by the photodiodes.